|Interactions||Strong, Weak, Electromagnetic force, Gravity|
|Antiparticle||Up antiquark (u)|
Murray Gell-Mann (1964)
George Zweig (1964)
−0.5 MeV/c2 2.3
|Decays into||Stable or Down quark + Positron + Electron neutrino|
|Electric charge||+2⁄3 e|
|Weak isospin||LH: +1⁄2, RH: 0|
|Weak hypercharge||LH: +1⁄3, RH: +4⁄3|
The up quark or u quark (symbol: u) is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nuclei. It is part of the first generation of matter, has an electric charge of +2⁄3 e and a bare mass of 1.8–MeV/c2. Like all 3.0 quarks, the up quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the up quark is the up antiquark (sometimes called antiup quark or simply antiup), which differs from it only in that some of its properties have equal magnitude but opposite sign.
- History 1
- Mass 2
- See also 3
- References 4
- Further reading 5
In the beginnings of particle physics (first half of the 20th century), hadrons such as protons, neutrons and pions were thought to be elementary particles. However, as new hadrons were discovered, the 'particle zoo' grew from a few particles in the early 1930s and 1940s to several dozens of them in the 1950s. The relationships between each of them were unclear until 1961, when Murray Gell-Mann and Yuval Ne'eman (independently of each other) proposed a hadron classification scheme called the Eightfold Way, or in more technical terms, SU(3) flavor symmetry.
This classification scheme organized the hadrons into
- A. Ali, G. Kramer; Kramer (2011). "JETS and QCD: A historical review of the discovery of the quark and gluon jets and its impact on QCD".
- R. Nave. "Quarks".
- A. Pickering (1984). Constructing Quarks.
- J. Beringer et al. (
M. Gell-Mann (2000) . "The Eightfold Way: A theory of strong interaction symmetry". In M. Gell-Mann, Y. Ne'eman. The Eightfold Way.
Original: M. Gell-Mann (1961). "The Eightfold Way: A theory of strong interaction symmetry".
Y. Ne'eman (2000) . "Derivation of strong interactions from gauge invariance". In M. Gell-Mann, Y. Ne'eman. The Eightfold Way.
Original Y. Ne'eman (1961). "Derivation of strong interactions from gauge invariance".
- M. Gell-Mann (1964). "A Schematic Model of Baryons and Mesons".
- G. Zweig (1964). "An SU(3) Model for Strong Interaction Symmetry and its Breaking". CERN Report No.8181/Th 8419.
- G. Zweig (1964). "An SU(3) Model for Strong Interaction Symmetry and its Breaking: II". CERN Report No.8419/Th 8412.
- B. Carithers, P. Grannis (1995). "Discovery of the Top Quark" (PDF).
- E. D. Bloom; Coward, D.; Destaebler, H.; Drees, J.; Miller, G.; Mo, L.; Taylor, R.; Breidenbach, M.; et al. (1969). "High-Energy Inelastic e–p Scattering at 6° and 10°".
- M. Breidenbach; Friedman, J.; Kendall, H.; Bloom, E.; Coward, D.; Destaebler, H.; Drees, J.; Mo, L.; Taylor, R.; et al. (1969). "Observed Behavior of Highly Inelastic Electron–Proton Scattering".
- J. I. Friedman. "The Road to the Nobel Prize".
- R. P. Feynman (1969). "Very High-Energy Collisions of Hadrons".
- S. Kretzer; Lai, H.; Olness, Fredrick; Tung, W.; et al. (2004). "CTEQ6 Parton Distributions with Heavy Quark Mass Effects".
- D. J. Griffiths (1987). Introduction to Elementary Particles.
- M. E. Peskin, D. V. Schroeder (1995). An introduction to quantum field theory.
- Cho, Adrian (April 2010). "Mass of the Common Quark Finally Nailed Down". Science Magazine.
When found in mesons (particles made of one quark and one antiquark) or baryons (particles made of three quarks), the 'effective mass' (or 'dressed' mass) of quarks becomes greater because of the binding energy caused by the gluon field between each quark (see mass–energy equivalence).The bare mass of up quarks is so light, it cannot be straightforwardly calculated because relativistic effects have to be taken into account.
Despite being extremely common, the bare mass of the up quark is not well determined, but probably lies between 1.8 and MeV/c2. 3.0 Lattice QCD calculations give a more precise value: ±0.14 MeV/c2. 2.01
At first people were reluctant to describe the three bodies as quarks, instead preferring Richard Feynman's parton description, but over time the quark theory became accepted (see November Revolution).
).quark model experiments indicated that protons had substructure, and that protons made of three more-fundamental particles explained the data (thus confirming the Deep inelastic scattering .Stanford Linear Accelerator Center However, while the quark model explained the Eightfold Way, no direct evidence of the existence of quarks was found until 1968 at the .strange quarks, and down, then consisting only of up, quark model (independently of each other) proposed the